Best available cop



Sept. 25, 1928. I 1,685,600

c. w. FREDERICK OPTICAL SYSTEM FOR COLOR PROCESSES Filed July 20, 1927 2 Sheets-Sheet 1 IN V ENTOR, C7zarZes Wfifederzd u, y $3. 8 w. m M

A TTORNEYS.

Sept. 25, 1928.

1,685,600 c. w. FREDERICK OPTICAL SYSTEM FOR COLOR PROCESSES Filed July 20, 1927 2 Sheets-Sheet 2 mmvroga,

Zes Wfiirederzdza, BY 4? #5 A TTORNEYS.

Patented Sept. 25, 1928.

UNITED-STAT PA E T OFFICE.

.cfimns w. rRiznERIcm-OF ROCHESTER, NEW YORK, ASSIGNOR T EASTMAN KODAK COMPANY,:OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

OPTICAL-SYSTEM FOR C OR PROCE SES.

"n iczitib n filed 1311 20, 1927. sr'iai' No. 207,2i3.

This invention relates to photographic color pi-ocesse s and more'particularly to a process disclosed in the patentto Bel-then, N 0. 99.2151, granted May 16, 1911, 1n which n filter with c0101 bands is placed at the ohjective and the exposni'eis made on a. sensitive em nlsion onthe rear side of zi support having minnt'e lens elementsnpdn its front snrfa'c'el' l "theredescribed; th e' 's :nne opt]- 051' system "is iised' for taking and pro ect ng and thecQloisci-een is pli c edint' the optica'l centertof the objectivef f WVh dilferent optical 'sy'st'emsare used, vii -ions expedients nrej'u'sed. to compensate "forthe 'difie rent,focgililengths of the taking undfpl oj ectingObject-lies. 'oii ted out in French patent tosoc'ieteDu 'ilin K D. 13 573 508, delive 'ed Ma1 ch 12;"1924 1s a feqni'reinentoffthe method that the filter as g0 'vieweil 'fr'oin'anyindivillitglxninnte lens ele- Practiczll considerixtion s render it; iii-genei'nl 'Hesi i'ableftht,j objeetjikes bf different .foc'allength 's'i be used en-d pti'rticnlarly that objectiiies "of ,"consi era'bl'y greater foc'iil len iised iii p iojecting' mjtion pietl'ir'es slight 'a dflis'finent 21's tli; fox "oi'd i nin'y meek mgvifi e I ivqr {Enid for color work. It i's,'thjeie'foife,-' desifieblethqt fefimttacliniefitsfsii'ch afiltrsofgieessorjlejnses, be iise'd-fid that 'hs'j zire necess'ary 1 be plaeed directly inlfro'ntifitli blijectiisjaili '-afcly iis'dfiiiitlio'u't requiring othei h'djnstmen't of'th'e apph'ifitll' i '1 1 I a tlfat this e111", he deems-58mm the folloiviilgivzi'jnif Kn'o"ivii igf' the piojeet'oi s sw eteme si th ppw iin'age oi the. polor seren'fis viewed f1"on' i the 'lent c'ula'ted .snrfa'cfjtli'ej filter'is soplnced on the taking" lensi iuid' at such .a d stance, in front of the frbntQmissj point that its appz i ent'irimge'zis'tiewed' fi'oin tlie f oc'alvplane will appear the s'iime' ,astheifilte'r to; be used in the projecting *s'ys'tein, 'thei'eb'y flilfil'ling the condition laid (low 9 in thelrencli pt'e'nt mentioned; butftthe s'az'ne tirnelo'catin the filte1's zit"points i emo'ved .fron'i theauss points; and iri frbnt'of therespect-ii e objectives, and 'also avoiding the use of supplementary or colli'mating lenses. A5; w'll he pointed out later, there are furength F of the system, iof -w ection systen used in ez rymg out my 1nvention;

' Fig.4 is a diagi'mnmgitic section of a preferred formof camerz object ve system used ii. line 'sereen instead of, i1 ,lenticnlated. stir- 'entiox'i' in'li si nple' 'way, certni'nqvell known lens system' 01 objective has images, a fayd1rected to tion in' line witli the "other. point.

iny' my AG emerges as- GC X 'zii'e' theiro'ntiiiiii'ieif focal points; isiOG' i this' will appeai'fron'i any point inthe' foczil plane peiii" to be' at G '1 'l f inoved fi-On'i'G't the in cz i iying nt-my invention. I

Figif'5 is a' diagram illustrating the use of nice o v s order to ei'p'la'in thetheory of my inoptical principles will be" first reviewed, A lens,- A tivo Gauss po1nts,"zind*in' the formation of I p p H one of' the Gz tiss points cme ges from' the system in 1'1 'pznallelfdirec- This in G and'G H and 136: as GKB. "The eluivalent focal ich Onnd' O t ote 'fol If thifobjecti ve has a. diaphm'g'm-op'ming HL' atlG hitting a vjilne $11911- zis'F/ r G and 'at"tlie .x is will snbtend the angle H'OL', '?An objectplzieed. at G: ivillj :i'pleft, thevirtualimagelof s'uch' :in'oliject ii'ill ti pl n dete 'inined hy'ithe 01 fi'oin the-object to G and f the distance from the virtual inmget-o GKQ. If tlie object occupy, the hme'CID, Where- 1G is less than half the focal length Fthe virtual image will appeal: to occupy the plane CID, l e tween O end I. lVhen I is very close to G, I is at a slightly greater distance fro n- G" and :IS I moves a\\-'zzyiroin G, I moves away more rapidly until when G'I is about equal faf systemh:1\-'ing the Gauss .points Bio "- i i i hi i its ag w l fill.

'itwill appear to ffill.

to one-half F, I, will be at 'O as Ithen moves to O, I moves from O to infinity at the left and becomes indeterminatej "When I is to the-left of O, the corresponding image becomes a real imagef'to-the-right of .The above isr'athei: le entaryoptics and ishere rerstated so as to render simpler and more readily understandable thepa pplicat-ion of ,these principles by my invention to thecolorprocesses{mentioned w If'Fig. 1 be considered a diagram illustr t -th Pi RQ Ii Q l prei t f ea ii thr' e"e l rg fiqeni-qtit ityn used in the said Berth'on process be placed at CD, its, virutaL image -then appear minj ah -lQ .P n.F' be at (I'D Q 1} this "screen iis of theg size ofthe h d a hr moac g'. he ept i e ee bi ie ivezte b s d 5 the 'lec i lai d i-t sls ze' o -t th r ii L- e'a 1 f: the ,eq qes neeeiz i Pesle ldete m ae .i t seve e-Re ects? Q 'difiet'entlfocat length ,a position, tor a screen i c i -iii i l i totalen t d e elf 'l e of thelprojlect-ion objeetive 2, drawn -th' i ti s; F ia mi n sz t d. a 'g" and, gf the 4 Gauss pointsbi ;aI' 1 objective having 'a.-'- fOCa1 18 I 1gt-h f equal; to ogQ-or .o fgi' The id-iaphragm is, indicated atllzl, and. hasthe same relatiyq, aperturev as d et, t eip iee ieii 'e i z vemidits e tual image will be atlfhf- Thezreqnired. ositlon an size 4 4. iii h i tual imagec'd of the screen being the same as that of CD of'Fig. lfjs kriowni that is io -=IO and Ord red); t; position at which a screened, equal sizeitoillt, nm tbe lace' d to produce 'thif virtual image" can e computed, or determined geometrically, by the method mentioned above, by drawing cfn'and dm pz'u allltoit-he 'axi s tofja line through '9 a-ndcand (lb'eing then theiintersections of oz/i and 0m with lines through it and'l parallel to the axisfl I It will be noted that the screen will be CID b'e'ot' thesame size over half the distance from-g to (5 and its virtual image beyond 0; i i

If, therefore, photographs are taken by an objective having the constants ot Figi 2, they may be projected through the system of Fig. l, and as the virtual image of the color screen is'ineach case the same,- as viewed from the image plane, the requirements of thb'cblouprocess are satisfied in this respect.

This discussion, it is to be noted, is general and is applicable to any types of lenses or lens systems. I In practice, I have found that, while al- 1nost any of the usual projection objectives may be employed such, for instance, as those ofthe well known Petzval type, or the objective disclosed in the patent of Altman and myself, No. 1,620,337, granted March 8, 1927,

certainknown types of photographic QbjC- tivesarebetter adaptedfor the camera than others; and in particulmyl'finddesirable an objective having a considerable thickness from iront surface torear surface and having {its front Gauss point r wellfbach-of its front surface so that the 7 corresponding :tront focal point 0 is-relativelyclose .to its front surface. i

, Fonpractical reasons it is desirable that the color screen be-elose to the actual front,

singface oftheobjective in both taking and gprojecting. v,This is'beca use' the front edge of the lens mount acts as a vignette'. Ifitbe placed at cc l its image vill appeal-latfiqd". If,1'how ever, it isto the right. 0t. ccl, ,i ts virtual image vill be, to the I will c'utdown theententto which the virtual image-pf theiscr'een is visible from n angle at thel gfocalplane. The nearer the screen comes; to;, coincidence vvith this front Q lens suriaceg or ;its mount, the its image t eici t whe .-v i9 h edges o t enposurefield, and thej be tter be' the resultant color rendering. This can be in larger than the diaphragm.-

,--. S ince the projection objective is n sedifa s thebasis, the filter or screen is nrountedas closelyas possible in front of it and .the position of the: virtuaL image ascertained. As just describedrithe location of the filter witl rf a taking objective of gii'en ifocal length isthen determined; To obtaixYt-he best results, there should. then beselecteda taking objective in-which the frontfsurtac e is located: just within the ascertained screen location, that is, an, objective having the front Gauss point well back within the objective.

Biway of illustration, examples of objecti vesuscd ingtaking and projection will no-\ begiven, but it is to be understood. that my invention is by no means limited to the objectives here shown nor do I herein claiz'n the formulae given.

A known pro ect-ion lens now on the marpart; obviated by. 1 making l the outer lenses lzet-and constructed in accordance with the patent't'o Altman-and myself, No. 1,620,337, March 8,1927, will be taken. This objective is supplied'with a focal length of 51 mm. and tin-aperture ot' F/2. Its front and rear Gauss points are located inwardly from the front and rear surfaces 13.6'and 13 3 mm; respectively; E lVhen the diaphragm is fully open, the mount may be considered as of unias'thediaphragin'of the mount; Its virtual form diameter as shown.' There is, there- -fore, in the'plane of G an'openin'g LH appearing to be at LH'. A screen S having three-color sections R, G and B is mounted as nea'r as practicable to the front surface.

-'lhis maybe at a distance-15.1 mm. in front of the front Gauss point, at the plane CID. This'screen has the same effective diameter imae e-CID' is then found to bein front of thc rear Gauss point G" by a distance of 21A-mm and to be distant 72.4 inm.fro1n the focal plane These points'and dimensions are shownin Fig. 3, the points being given the'sainereference characters as in Fig. 1. The'screen- S -in practice has sheet gelatine elenients inoulited betiveen plane glass plates 1 ,1 4 The objective-chosen for the taking camera :is illustrated in-=Fig:4.' This is' a niodificationJofa'akno v-n typezof objective; the actual forxirulasixsed: being as' follows a? Dune P In th'eg'above table I) to esignat'e the succesive 51BX15 elements from: front to back,

R, to-R theradii-ofcuuvature for-the successive' surfaces, T} .to T the thicknesses and SfgtmSfiathe separations; :The; index ofw're- :fra'ctibncfonthe Dwline' and-the dispersive ratio v are-'alsorgiven. For-the four positive lenses barium crown glass is =us'ed; and for 'thatvvo' negativesydenSeflint;

Its frontiGaiisspoint is 13.'7-1mnr;zbehindthe mmsandais usedtatla relative apert uieof F72.

- front surface, and: its-rear .Ga-uss'fpoint is SLS mini in front of its rear-surface. -lt-is to. be

--n"oted1 thatthe; front. Gauss point is, therefore,-rac'tuallyin:back oftherear Gauss point.

- Since the desired positionof'the virtual i'imag'e of=azscreenisknown-to be 72.4: mm.

in front of? the focal plane, the required position of the actual screen is-readily 'deter- -niincdv-and is found-to lJCl? mm. in front It is to be-noted that my invention is applicable tosystem's ofwidely ditl'erent types,-

of G, or 3.3 mm. in front of the trout surface. In practice, this is carried in a cap adapted to be slipped on the front of a mount and positioned accurately atthe desired position, as, for instance, by the struc-t" ture shown in a copendine application of Otto lVittel, Serial No. 189,131, filed May 5, 1927. i

As has been stated, the theory outlined is general in its application but when the taking lens has a focal length materially shorter than the projection lens. a camera objective having the characteristics of the aboveexample is pm-ticularly useful. The front Gauss point is so far behind the front surface, that the latter is brought relatively close to the front focal point, making it possible to position the color screen nearer to -the front focal point than to'tho front. Gauss point and,- at the same time, so close tothe front surface that it is not greatly vignetted thereby. This characteristic is inosteasily attained in a properly designed objective of considerable thickness from front to rear,and the front Gauss point is found to be well behind the central point of the objective, being in this case well behind the: rear Gauss point also.

'It is' to be notedthat theltwo objectives have'tlie same relative aperture and since,

in-each case, the effective diameter-0t the color'screen' is thesame as that :ofthe diaphragm, theirrelative diaineters have the same ratio as the-focal Iengt-hsof the-Ob- These are shown ;onan neighborhood offithe" central planet-of; the

focal; -len th an'dmpertu re and is, in fact, general-1m its apphcatxonr: 1

The: systemwith which it is --uscd 3 may .be of the type using a line screen or a screen havni'g minute apertures: n: place- 'of lenscs,

such a system being shown'in Fig. 5,'where ,5 is the objective,'6 thei screen,-v7- a transparentI-support-"with an .emiilsion S, and9- a veryfinel'y perforated opaquev screen sepa- "rated'f-rom the-emulsion and-liere-shown as- --.in contact with the'front surface of-the support 7.

It is obvious thatthe invention is applicable to-awide range of structures and I consider as includcdin 'n'lyinvention all such modifications andequivalents as fall within 'the scope ofzthe appended-claims.

Having thus describedimyzinvention,what I claim .as new and desire :to secure by Let- '5 ters Patent is:

1-. A photographic optiealsystem =fr'use in :the vform-itigm, .in la =.photographic :layer having associated therewith numerous'lmiero'scopic-image forining:elements;of minute .'10 photographic images-for. projectibnithrough positioned in .front of the fphotographic objective at: that :poirit whiclreisxeonjugatedo .a point distant froniithe rcarifocaliplane of :the objective; bygthel distance ;.wh ich-zthe said virtual image in :the: projection system: isj dis- -.jection objective."

1 *2. A photographic zoptieal systenr rfor use in the formati0n,.:in an phptographicilayer having associated 5 therewith numerous; mi-

.80 croscopic image -formingielementsgof minute iphotogr aphlic images-efbr action; through .a 2 pro ection; system comprising a -pro eet 1on *Ob]eQtlVe".'.and' 11a polyehromatrc. screen; (the virtual E1mage.-o which :oocupzes 5.3.11 :ascer- .435 tained position withere'specfitostheirearifodal plane 'of objective;- :said photographic :optieal ,zsystem comprisingiaa:iphotographic positionediin front tofrztheiphotognaic ob- :jective :ataftlhat point whichrissconju late to aaipointfilis'tant'ffromi the rearifo'eal p aneof 5 the objective th'ea'il-istance whielil the said avirtualiiina rain the projebtion systeiqiis distantifronitlie rear -tocal' plane bfi thei projecti'on objective? the:'=efiec'tiv'e-= diameter bf the second mentioned screen having the same ratio toi the first. .m'entioneiduscreem that: the

.efqcal :length? of'.-.the" photographic objective :to .that: of1the-aprojectioniobjective,

whereby the virtual=.:image: in th aphotographic system has; theis'amesizeand rela- :stive :positiomasthat in the projection system.

3. ,:'A=, hotognaphic: .optical .system-;for use in i the. oi'ination, a photographic .laye r having. associated therewith mill-morons mizcroseopic imagef-iorming elements,-.o-m1nute same size and "relativ jective, said photographic optical system pris ng p grap i o lec iv having a focal length less than that .of the projection objective but of the same relative aperture and a polychromatic screen similar to the first-namejd'screen and positioi edin front of the photographic 1ObjeQtlV at that point which is conjugate-ton pointdistant ifrom the .rear focal plane of the objective 'bythe-samedistance as the first mentioned with respect :to the ,rear -;focalplanehof such objective,saidphotograpliic. optical sys- :tem' comprising a photographicobjective:

.havinga focal length Jess than-,that-zof ',-the projection objective but of the same relative -apert,ure.ai1.d a 'polychromatic .scr'een similar -t.0';:the first-named screen .Zand ipositioned -in frontof the photographic objective 2 at that point which .-is-eo1ijuga t e: toa; point distant from the rear focal plane of the objective b y ith e same distance as the first mentioned nseifeenis from the rear focal plane of the projectionobje ctiv e, the effective diameter. of. the second. mentioned. screen. bearing the samematimtothat of the first menobjective pf-difierentiifoeal length frornzt-he :project-ion objective; and a: polychromatic screem similarrto thesfiist-naihe'd screen :and 5 tioned screen that;';1th 'e jipcal "length of the P Q Phi iQ iQ tibieerst th tef'th projection l-lobjective', .-.\j'bel'eby the virtual image in thei' iphotpgraj ihic' system .has the iios tic as that i thep eie t iinsnt m 5. A photographic optical system for use .rin ztheziovination, aiphotographicdayer;

having associated. therewith mumerous --microscopic image -forniing'i element's, of mi- =nute photographic images mfor pro ection through aYprojectionsystem comprisingva length and a a polychromatic ;sc'reen.-. situated ii n front of said objective; the-virtual image of the screen o'cciipyinganascertainedsposltion. with =respect: to the rear {fbcal' 1 plane of -'such objective, said. photographic: optical system-comprising a photographic? objective having. a focal lengths less: than: that of: the .projection ohjectivebut of the. same relative aperture and a pol-ychromatic screen similar 'to the first-named screen :and positioned in- =front o'fitlie photographic objectiveat that point which is conjugate to'apoint distant -fromthe;rear.focal plane ofthe objective bythe same distance as. the first mentioned screen isdistant-from the reanfocal plane -.-pro.jectioniobjective. of'- ascertained l-iocal llo ofthe projection objective, the front Gauss point of the photographic objective being behind the front surface by a distance exfirsbnamedscreen and positioned in front,

cceding half :lzr-

of the bjrcii :c, and the screen being nearer to the front focal point than to. the f1T0 t'Gauss point.

"6.1K photographic optical system for use in the formation, in a photographic layer having associated therewith numerous microscopic image-forming elements, of minute photographic images for projection through a proj ection system comprising av projection objective of ascertainedffocal length and a reg h ea i ise e s te in ro 9 Sal '-l 1 th v tP t-i o he s r we pa n mo ies 'ro'sitif \v ithlj-respec t icrezinjfooaljplane of .sucli emr e.r t 'eiih eipbiw e a neafocallength less thangthat' of the projection objective .but. of;.. .th'e; same relative aperture.

and a polychromaticiscreen similar tothe of the photographic obj active =at that point which. is. ;con ugate. to a a pint, distant from theIrear focalplaneof t e, objective by the same; (listance as the first; mentioned screen isdistant. from the reanfocal .plane of theprojection. objective, the front surface of t e. plietarevh a abi ctrt b n the front focal point than tothefront Gauss po nt; and ,the screen Being situated between the. front surface. ,the I front "point m nu an tegi apl p ma es f 7. A photographic opticalfsystemrfor-us e in .the formation, in a. photo raphie; layer haying-i assQciated' .therevvitg n1imer ous li s p e.im g -f rming nps i f n. h e a nreasetwne etsma aeapr sins a proj ac o .bi e r of 1 a ee t lw da {Peal length and, :a polychrornatic screen situated in front of saidobjecti-v e, thewiitualimage of t e sem c py n .anes rt eed re ir tion withga-espect to -the rear..- focalfialane' .of'

such objective, said; ,pl;i;otogra; hie,- optical s e -s me e. ph er l O je e having-a focal lengthlessthamthatpf the projection objective but; of the'samerelatiye aperturefaudz a polychrgmatic screen similar' to the lfirst named screen. and positioned in front of the photographic gobjectivez at that p int whi h :is z o ing ei po n d n from the rear focal plane of the objective by the same distance as the first mentioned screen is distant from the rear focal plane of the projection objective, the effective diameter of the second mentioned screen bearing the same ratio to that of the first menioned screen that the focal length of the photographic objective bears to that of the projection objective, and the front surface of the photographic objective being closer to the front focal point than to the front Gauss point and the screen being situated between the front surface and the front focal po1nt. I I

P Q graPhic optical system for use in a color photographic process for taking pictures. on a photographic layer having associated therewith numerous microscopic image-forming elements and comprising an objective having its'front Gauss point over half the actual length of the objective behind its front surface'and 'a polychroinatic screen positioned'in front of the objective nearer to the front focal point than to the front Gauss. point thereof.

91A photographic optical system for use in a color photographic process for taking pictures o'n a photographic layer having as es e dft fir vifl merqu m s p m g eie' rm aef le andp mr is an ohjective'havingjan actual ;len th exceeding a .'.-1 fi .f a .l .h L d-Theme its "from Gauss" point over 'al'f its' a'ctual length behind its front surface pa-:1; polychroinatic screen positioned in frontof the objective nearer-to the front focal pointth'an to the front Gauss point .thereof. I

V 10.v A photographic optical system for'use in a {color photo raphic process for taking pictures on a p oto'gra'phic layer having associated therewith numerous microscopic m g bi in el 3 sp nif' s fi a objective having its 'front Gauss ,point he hind IQ3lX F Po t. n in i' ychromatic screen" ositioned in front of it nd'aa r'oia' an vipei pe 't n to is'f 1font Gaus s. oint'. f"-

i 11. AJITOPtiCaLSYS m id 111 6 ill-316010? f' c' ""rocess' for'takingpictures on a photographic; layer having associated. therewith numerous microscopic. mageelenientjs and jco'mprisingan objective: having'its'frontsurface nearer to its front focaljipoint than to i ts-.front }auss point, and a polychromatic screen positioned in frntf of it: behindifi'ts front focal P n -I 7 f i optical' systein for' u'se i nja col'or photographicproce ss for tak ng pictures on a Ph t ph ye 3 m e l ie thereivith numeroug, microscopic image forming elements ,cjompris 'ng anlob ec me; amaze its. r' fi-' .j re e g r iitlk d poin t n. 9. it from 1 Gau s point aiid a polych'romatic screen positioned in front of it and behind its front focal point, whereby a virtual image of said screen is formed in front of the front focal point, the exact position of said screen being detcrmined in accordance with the constants of a projection system by which pictures made by the objective are to be pro ected and being such that the said virtualimage will be of the same size and position as the virtual image of a correspon mg screen in the projection system.

13. Complementary optical systems for use respectively in the taking and projecting of color photographs by the use of photographic layers having associated therewith numerous microscopic image-forming elements and comprising two objectives of different focal. length and two similar polychroniatic screens, one screen being mounted in front of each objective, the positions of said screens being such that the virtual images of the screens areof the same size and have the samepositions relative to the rear focal planes of said objectives respectively.

14. Complementary optical systems for use respectively in the taking and projecting of color pictures by the use of the same photographic layer having associated there'- with numerous microscopic image-forming elements. and comprising t'woobjectives' of different focal'lengths but of the same relative apertureand two similar polychromatic screens; one'screen being mounted 'in front of each objective-r, the positions of said 5 screens being suchthat the virtual images thereof are of the same size and have the same positions relative to the rear focal planesof said objectives, the relative. sizes of' the two, screens being the same as the relative. focal lengths of the two objectives with which they are respectively associated.

15. Complementary optical systems for use respectively in the taking and projectint, ofcolorphotographs by the use of the same photographic layer having associated therewith numerous microscopic imageforming' elements and comprising, as taking'systein, an objective having it'sTf'ront rfac closer teth rom ocal p nt. th n to the front Gauss [point andi'a polychromatic screen mounted between the: front surface and t-he frbnt 'focalpoint'whereby there is formed in front of the frontlfoca'l'point s1 virtual image of the said screen having a definite size andposition relative to the rear focal plane of the saidobjective and further comprising, as a projecting "system, an objective of (greater focal length than the first i rnentioned objective and a polychromati c screen similar 'to" the; first mentioned screen andfp'ositioned in front of said obj'eef tive 'at .a position slich its virtual image has the same size and position relative to the rear focal plane of the objective as the first mentioned virtual image has to the corresponding focal plane of the first system.

16. Complementary optical systems for use respectively in the taking and projecting ofcolor pl'iotographs by the use of the same photographic layer having associated therewith numerous microscopic image-forming elements and comprising, as a taking system, an objective having its front uriace closer to the front focal point than to the front Gauss point and a polychromatic screen mounted between the front surface and the front focal point whereby there is formed in front of the front focal point a virtual image of the said screen having a definite size an'cliposition relative to the rear focal plane of the said objective and further comprising, as'a projecting system, an objective of greater focal length than the first mentioned objective and a polychromatic screen similar tothe first mentioned screen and positioned in the front of said objective, infront of the front surface of the objective and behind the front focal point by a distance greater than one half the focal length of the objective at a point such that its virtual image is positioned behind the front focal point and has the samesize and position relative to the rear focal plane of the objective as the first mentioned virtual image has to the corresponding focal plane of the first system."

17;In' acolor' process involving the use of'aphotographic layer having microscopic image-forming. elements] Zassociated therewith; the steps ofiformingf in such a layer an image by" means of an objective having in front thereof polyc'hro'matic screen the virtual {image of, which has a definite size and'position with respect to the layer; and projecting the image resulting in such layer from such exposure through an objective of a different focal"length "havingin front thereof a similar screen'a't such a position that the virtual image thereof has the'same definite size a-nd'position with respect to the layer as .the' first mentioned screen had.

Signed'at Roche-sten'NeW York, this 16th dayof July, 1927. v

' CHARLESWVLFREDERICK.

lOO 

